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Computer Program Clears the Static

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When Islanders hockey fans gazed up at the banners and retired jerseys displayed at Nassau Veterans Memorial Coliseum on Long Island, they connected with a history of the team and the sport. But when the names and numbers of players on the ice were read over the public address system, the people in the stands were suddenly disconnected. The 20-year-old sound system produced only garbled squawks.

The stadium had, as general manager Lance W. Elder put it, ''an intelligibility problem.'' And after private suites were installed in the early 1980's, Mr. Elder said, the new structures blocked all public-address sound to the top five rows, about 720 of the coliseum's 18,000 seats.

The question of what to do was answered by a computer program for sound modeling and acoustical prediction, called the Auditioner, from the Bose Corporation, a privately held company based in Framingham, Mass., better known for its line of stereo speakers.

Nine years in development, the Bose Auditioner system combines information about the materials and measurements of a room to replicate existing sound, then forecasts how that sound might be altered by changing certain acoustical factors.

Its detractors, particularly among those who have long practiced the art of acoustics without computers, argue that it is less an acoustical modeling program than a clever marketing device to sell Bose's core product, speaker systems. Indeed, carefully focused and directed speakers are integral to Bose's cure for an acoustically sick space.

But it is a cure that has won converts since it went on the market in 1995. Auditioner has been used to clear up problems in the Sistine Chapel in Rome, the European Parliament Building in Brussels and assorted public spaces in this country.

Rival companies have used similar technology in other big jobs. JBL Professional, a Northridge, Calif., unit of Harman International Industries Inc., used some digital technology, though as a supporting tool, when it handled sound reinforcement for the Sydney Opera House.

In JBL's system, as in most others, digital technology is secondary, a method of checking the work, not planning it.

Where Bose breaks from traditional practices is in making digital modeling central to the process. It is usually the system's ability to replicate troubled acoustics that wins potential clients' confidence in its ability to fix them.

Recreating the sound of an existing acoustical environment is a two-step process. First, vast amounts of data are fed into a computer -- the size of a space, the materials used to build it, its surface contours -- so that a ''virtual'' acoustical environment can be constructed. Second, recordings of speech and music, produced in a resonance-free space are played into that computerized acoustic, which mimics the sound alternations of that environment.

That second step gives Auditioner its name. The compact, table-top unit consists of two small loudspeakers flaring out from a platform on which the listener rests his chin. The speakers are placed close to the ears, keeping out extraneous sounds.

Mr. Elder said Bose's version of the acoustical anomalies in the Nassau Coliseum was ''as close to a perfect replication as one could hope to achieve.'' And so when Bose came up with its acoustical model of what the corrected sound would be like, Mr. Elder said, he believed it enough to invest $400,000 in the arena's acoustical makeover.

But some outside observers cast a jaundiced eye on the Auditioner's abilities.

''We are not yet at a state where we can measure and duplicate and model acoustical spaces to the fine degree that human hearing is capable of discerning,'' said Thomas M. Young, a sound and communications systems consultant with Artec Consultants Inc. of New York.

''Many companies have developed in-house computer auralization programs,'' he said. ''We all use them for research and prediction, almost as a second opinion, but we do not base our designs on them.''

Mr. Young criticized Bose's use of the Auditioner as ''a marketing tool to sell their sound systems.''

Noting that his own company does not manufacture products, Mr. Young said: ''We employ our ears, experience and intuition. We don't rely on that kind of witchcraft.''

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Kenneth D. Jacob, Bose's chief engineer for acoustic research, hardly sees his system as black magic. It is a product, he says, of long, slogging programming work.

''I have to admit I underestimated the difficulty of what I wanted to do,'' he said. ''There are millions of interactions between a given sound and the room in which it occurs. That was the body of our research, measuring those interactions.

''But we soon discovered that if you try to do the math of all those interactions, not even the world's most powerful computer would finish in our lifetime.''

The breakthrough came when the Bose team learned how to reduce the amount of math required. Instead of charting all possible combinations of sound, the Bose team relied on perceptual coding -- trying to fix only the problems most people could hear, and ignoring subtle effects. For five years, Bose pruned unnecessary data from the program, guided by the acoustical changes an actual jury of listeners could or could not hear.

While such an approach might fall short of pleasing the ears of a trained musician on the fine points of concert-hall acoustics, it does seem to do the trick in many public spaces.

But some spaces, like subways and airport terminals, can be acoustical nightmares, Mr. Jacob said. Only architectural changes -- or, at a minimum, the use of sound-deadening materials -- can make audible the announcement that Flight 203 has been moved to Gate C14.

Other large spaces can be more manageable. Scott Ellison, director of athletic facilities at the University of Minnesota, recalls when Mariucci Arena, home of the Golden Gophers hockey team, opened in 1993. Some 9,000 fans jammed the arena for an exhibition by great figures from the modern history of Minnesota hockey.

It cost another $90,000 to fix the problems using the Bose system. ''We thought the modeled version of the corrected sound was really promising,'' he added, ''but the actual result was even better.''

Auditioner has also faced more delicate challenges. The St. Louis Abbey, a Benedictine monastery in that Mississippi River city, chose the Bose modeling system to redeem the sound of its architecturally celebrated church, which is formed by stacked rings of soaring arches.

''It was impossible to understand anything,'' recalled Julie Constantino, director of development for the church. ''I guess that's what it must have been like to go to church when the Mass was given in Latin.'' Since the makeover, she said, the quality of sound has improved noticeably.

But other observers are hesitant about unqualified endorsements. ''Auditioner is good for getting a general idea of sound coverage but beyond that, it's pretty iffy,'' said Elizabeth Cohen, consulting professor of electrical engineering at Stanford University.

''I'm not sure it's really all that more precise than the tabletop cardboard model acousticians have used for years. You place Mylar on surfaces and, pretending that sound behaves like light, you shine a laser light on the shiny texture to show reflection patterns.''

One of the highest-profile assignments for Auditioner has just been contracted: a $500,000 revamping of the 20-year-old sound system in the Louisiana Super Dome in New Orleans, to be finished in time for the Saints home game on Oct. 6. The Super Dome will be host to Super Bowl XXXI next January.

''By today's standards, our present sound system really doesn't offer suitable fidelity or coverage,'' said Wayne W. Griffiths, electronics systems superviser for the state-owned Super Dome. ''We have areas where the sound is too loud and other places where you can barely hear.

''When we listened to Bose's model, they demonstrated what the sound would be like from different seats in the stadium. The volume levels and intelligibility stayed the same in every area, all the way to the top.''

A version of this article appears in print on September 2, 1996, on Page 1001040 of the National edition with the headline: Computer Program Clears the Static. Order Reprints|Today's Paper|Subscribe